Ventilating exhaust fans, such as those typically installed in bathrooms, draw air from within a space and pass the exhausted air out to another location, such as by passing the exhausted air through a vent in the gable or roof of a building. Exhaust fans can include a rotating fan wheel having a plurality of vanes that are rotated in a housing to draw an inward airflow from the space through a housing inlet and push an outward airflow through a housing outlet to the other location. Exhaust fans are typically mounted in an aperture of a wall or ceiling of the structure separating the space and the other location by mounting the housing to wall or ceiling joists or other structure in the wall or ceiling.
Certain ventilating exhaust fans include backdraft dampers positioned at the housing outlet to allow the outward airflow through the housing outlet while preventing airflow in the reverse direction. Although backdraft dampers can mitigate backdraft through the housing outlet, often at least some portion of the damper assembly partially obstructs the housing outlet reducing the effective cross-sectional area of the housing outlet. The reduced cross-sectional area of the housing outlet reduces the efficiently of the exhaust fans by obstructing the outward airflow. In addition, the disruption of the airflow from the backdraft damper can amplify noise emission and audible noise generated during the operation of the ventilating exhaust fans. In particular, the shape of the backdraft damper can reflect sound through the ventilation assembly housing amplifying the noise. Similarly, the backdraft damper can be vibrated by the exhaust airflow or pushed against surrounding housing creating additional noise.